s=input("一串字符：")
res=True
if s.isspace() is False:
   i=s.lower()
   r=i.replace(" ","")
   if r.isalnum() is False:
       print("含有非法符号")
   else:
       low = 0
       high = len(s) - 1
       while low < high:
           if s[low] != s[high]:
               res = False
               break
           low += 1
           high -= 1
       print(res)
else:
    print(res)



